Biopsy is the removal and study of body tissue for medical diagnosis. Physicians in many specialties commonly obtain biopsy samples of a target tissue area from patients in order to detect abnormalities such as cancer. When physicians must access a biopsy location inside a patient's abdominal cavity, thoracic cavity, or gastro-intestinal system, an invasive procedure is necessary. For such procedures, physicians often use an endoscope to avoid more traumatic open surgery. Generally, modern endoscopes are long flexible instruments having a light source and an image sensor for visualizing the interior of an internal region of the body. In addition, endoscopes commonly have an accessory or working channel though which another device, such as a biopsy device or a tissue anchor delivery device, can be advanced toward the target area. Alternatively, an external accessory channel may accompany and be used with an endoscope.
When a medical professional wishes to obtain a cellular tissue biopsy sample, one common procedure he or she may perform is fine needle aspiration, or FNA. Aspiration is a suction process that removes a tissue sample that is suitable for examination under a microscope. Generally, a hollow fine gauge needle engages the tissue and a syringe or comparable device sucks the tissue sample through the needle or needle system by creating a negative pressure between the syringe and the sample. Various types of hollow needles are used in an aspiration biopsy to obtain the tissue sample, such as a beveled needle, a ball-tipped needle, or a dimpled needle. U.S. Patent Publication No. 2006/0116605 discloses a needle having a spoon-shaped configuration in which rotational movement of the needle scoops a sample of the tissue during aspiration.
Biopsy devices configured for an FNA procedure generally further include an outer sheath containing a sheath lumen in which the needle is slidably disposed. The sheath protects outer surroundings, such as the working channel of the endoscope, from the sharp end of the needle as the biopsy device is advanced toward the target area. During advancement of the device, the needle remains completely within the sheath. At the target area, the distal end of the needle extends beyond the outer sheath to pierce the tissue and obtain a sample. The needle retracts inside the sheath after the sample is taken.
When obtaining a tissue sample that is larger than a cellular sample is desired, it may not be preferred to use an FNA procedure. Rather, a biopsy system that comprises a cutting cannula and stylet assembly may be used. The system is operated using a spring-loaded handle of the type disclosed in U.S. Pat. No. 5,538,010, the disclosure of which is incorporated herein by reference. Another biopsy instrument utilizing a stylet and cannula assembly is the QUICK-CORE™ Biopsy Set, manufactured by Cook, Inc., Bloomington, Ind. The inner part or stylet has a sample collecting element or notch formed near a stylet distal end. The distal end of the stylet is driven into the target area, and the tissue prolapses into the sample collecting notch. Thereafter, a spring-loaded cutting cannula is rapidly advanced distally into the underlying tissue and thereby cuts the portion of the tissue disposed in the collecting notch. After the sample is cut, the stylet with the retained sample and the cannula covering the stylet are retracted from the target area.
Although the biopsy systems having a collecting notch are used to obtain tissue samples that are larger than cellular samples, such tissue samples are still of limited depth. Also, the tissue samples must be taken from the side. As a result, displacement of the tissue sample may occur when retracting the stylet. Thus, there exists a need to obtain deep core samples taken straight on, and there exists a need for a more secure attachment of the sample. Additionally, the stylet and cutting cannula of these biopsy systems are both configured to pierce, shear, or cut tissue. Unlike the outer sheath of the biopsy device configured for the FNA procedure, the outer cutting cannula does not function as an adequate sheath and can damage the working channel of the endoscope or bodily tissue. Thus, there exists a need to protect the outer surroundings from the cutting edge of the cannula.